Subject Re: FB database in RAM
Author fabianchocron
Hi Kjell

We have been doing something similar to what you are trying without having to take the risk of running the DB in Ram, let me explain:

In FB 2.1 64 bits (for Windows) we have been running the superserver version, with a very large DB. We configured the FB server to run about 2 GB of cache in ram, and set many other FB config variables to enhance performance. FB 2.1 64 bits has a limit of how much cache it can hold in ram, I think that is 2.5GB if I remember correctly. The limitation does not make any sense as the OS is 64 Bits and should be able to handle much more (from memory 32 bits OS can handle 2 potency of 32, been 4 GB, and 64 Bit OS would be 2 potency of 64, been a number I cannot even imagine). Any-ways, running the DB in ram is very risky, and you can avoid it by just placing a big cache on the FB configuration, and have a Server with 64 GB ram, and configure the RAID controller to allocate 100% priority to read cache. If you have a good RAID configuration, say 8 HDD on Raid 6, the reading speed would be 6 x HDD speed, and today you can buy SAS HDDs with very fast reading capabilities. I also think you may be able to have the DB file actually cached by the OS (for reading purposes) instead of having FB doing so, then why risk it?

I am not sure if FB 2.1 64 for Linux has the same limitation in terms of the cache, it may be worth checking it,


--- In, Kjell Rilbe <kjell.rilbe@...> wrote:
> Hi,
> For performance reasons we're considering a setup where our 50+ Gbyte
> Firebird database would reside on a RAM-disk.
> I'd like to hear if anyone else has had experience with running large FB
> databases in RAM. Any problems? Performance compared to disk based? Any
> gotchas?
> The server has strong UPS at our hosting company, so we will accept
> nightly backups as "good enough". Backup would be done by bringing the
> system offline and copy the fdb file (currently not using nbackup due to
> an unresolved problem that we suspect was caused by nbackup). backup
> will be made both to local disks and to a remote rsync volume.
> The server is a Win 2008 web server, 64 bit.
> The current setup is with two RAID 1 volumes, one with OS, app etc, and
> the other with the database file and nothing else. Write cache enabled
> on the disks and forced writes off in the DB.
> Thanks,
> Kjell
> --
> ------------------------------
> Kjell Rilbe
> DataDIA AB
> E-post: kjell.rilbe@...
> Telefon: 08-761 06 55
> Mobil: 0733-44 24 64
> [Non-text portions of this message have been removed]